报 告 题 目：Quartic bosonic metallic state and it’s topological properties

主 讲 人：Julien Garaud

单 位：法国图尔大学

时 间：3月2日18:00

ZOOM ID：210-089-8623

密 码：123456

摘 要：

Superconductivity is an ordered quantum state with a long-range coherence of pairs of electrons, the Cooper pairs, which leads to zero resistivity and diamagnetism. I will present the recent observations of a new resistive state, coined quartic bosonic metal, characterized by the absence of long-range order between Cooper pairs but with order between pairs of pairs. Unlike the superconductors, which break the U(1) gauge symmetry, this state spontaneously breaks the (discrete) time-reversal symmetry, and exhibits unconventional magnetic properties. I will demonstrate that the quartic bosonic metal state can be effectively accounted for, by a Faddeev-Skyrme-like model for the four-fermion order parameter. Its spectrum of topological excitations is rich, as it hosts domain-walls, magnetic-flux-carrying skyrmions, and most likely hopfions.

简 介：

Julien Garaud graduated from University of Tours, France, is a professor at Institut Denis Poisson (IDP), at the University of Tours, France and is has adjoint affiliation at Nordita, Sweden. He has been a postdoc at Massachusetts University, Amherst, USA and the Royal Institute of Technology of Sweden (KTH) in Stockholm. Julien is an expert on vortices and skyrmions in multi-band superconductors, as well as in numerical computations. He has more than 30 publications in Nature Physics, Physical Review Letters, Physical Review B, and Nuclear Physics B.